STR: 1. Search a keyword, "co" in Preferences page. Expected: The tooltip bottom arrow of menulist doesn't match the spec[1]. Actual: The potions is not correct. See it in the "tooltip-position-is-not-correct.png" attachment. [1]: https://mozilla.invisionapp.com/share/X8BGCX9PD#/screens/245814067

To be more specific, the tooltip position on menulist is different with on button. It might be due to the difference of element height or margin. We're currently using extra hbox wrapping around button or menulist element to position the tooltip, so the surrounded hbox will be affected by menulist/button margin undoubtedly.

The root cause is due to menulist & button alignment in preferences.inc.css. Fixing the alignment issue can fix this tooltip position issue as well. It seems like the tooltip position issue can be treat as a visual issue and be fixed within bug 1398050. This might be able to a dup as bug 1398050, and we can reduce the effort of creating additional bug dependency for fixing just a small css changes.